Power control for communications systems utilizing high speed shared channels

ABSTRACT

A system, components and methods provide controlled transmitter power in a wireless communication system in which both dedicated and shared channels are utilized. A network unit preferably has a receiver for receiving UL user data from WTRUs on UL DCHs and at least one UL SCH and a processor for computing target metrics for UL DCHs based on the reception of signals transmitted by a WTRU on an UL DCH associated with an UL SCH usable by the WTRU. A shared channel target metric generator is provided that is configured to output a respective UL SCH target metric derived from each computed UL DCH target metric. Each WTRU preferably has a processor which is configured to compute UL DCH power adjustments for an UL DCH associated with an UL SCH as a function of UL DCH target metrics computed by the network unit based on the reception of signals transmitted by the WTRU on the UL DCH and UL SCH power adjustments for the associated UL SCH as a function of the respective UL SCH target metrics output from the shared channel target metric generator. Preferably, the target metrics are target signal to interference ratios (SIRs).

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority from U.S. Provisional PatentApplication No. 60/419,380, filed Oct. 17, 2002, which is incorporatedherein by reference.

FIELD OF THE INVENTION

The present invention relates to methods and apparatus for power controlin wireless communication systems and, in particular, systems which usehigh speed shared channels.

BACKGROUND

Wireless telecommunication systems are well known in the art. In orderto provide global connectivity for wireless systems, standards have beendeveloped and are being implemented. One current standard in widespreaduse is known as Global System for Mobile Telecommunications (GSM). Thisis considered as a so-called Second Generation mobile radio systemstandard (2G) and was followed by its revision (2.5G). GPRS and EDGE areexamples of 2.5G technologies that offer relatively high speed dataservice on top of (2G) GSM networks. Each one of these standards soughtto improve upon the prior standard with additional features andenhancements. In January 1998, the European Telecommunications StandardInstitute—Special Mobile Group (ETSI SMG) agreed on a radio accessscheme for Third Generation Radio Systems called Universal MobileTelecommunications Systems (UMTS). To further implement the UMTSstandard, the Third Generation Partnership Project (3GPP) was formed inDecember 1998. 3GPP continues to work on a common third generationalmobile radio standard.

A typical UMTS system architecture in accordance with current 3GPPspecifications is depicted in FIG. 1. The UMTS network architectureincludes a Core Network (CN) interconnected with a UMTS TerrestrialRadio Access Network (UTRAN) via an interface known as Iu which isdefined in detail in the current publicly available 3GPP specificationdocuments. The UTRAN is configured to provide wireless telecommunicationservices to users through wireless transmit receive units (WTRUs), knownas User Equipments (UEs) in 3GPP, via a radio interface known as Uu. TheUTRAN has one or more Radio Network Controllers (RNCs) and basestations, known as Node Bs in 3GPP, which collectively provide for thegeographic coverage for wireless communications with UEs. One or moreNode Bs are connected to each RNC via an interface known as Iub in 3GPP.The UTRAN may have several groups of Node Bs connected to differentRNCs; two are shown in the example depicted in FIG. 1. Where more thanone RNC is provided in a UTRAN, inter-RNC communication is performed viaan Iur interface.

Communications external to the network components are performed by theNode Bs on a user level via the Uu interface and the CN on a networklevel via various CN connections to external systems.

In general, the primary function of base stations, such as Node Bs, isto provide a radio connection between the base stations' network and theWTRUs. Typically a base station emits common channel signals allowingnon-connected WTRUs to become synchronized with the base station'stiming. In 3GPP, a Node B performs the physical radio connection withthe UEs. The Node B receives signals over the Iub interface from the RNCthat control the radio signals transmitted by the Node B over the Uuinterface.

A CN is responsible for routing information to its correct destination.For example, the CN may route voice traffic from a UE that is receivedby the UMTS via one of the Node Bs to a public switched telephonenetwork (PSTN) or packet data destined for the Internet. In 3GPP, the CNhas six major components: 1) a serving General Packet Radio Service(GPRS) support node; 2) a gateway GPRS support node; 3) a bordergateway; 4) a visitor location register; 5) a mobile services switchingcenter; and 6) a gateway mobile services switching center. The servingGPRS support node provides access to packet switched domains, such asthe Internet. The gateway GPRS support node is a gateway node forconnections to other networks. All data traffic going to otheroperator's networks or the internet goes through the gateway GPRSsupport node. The border gateway acts as a firewall to prevent attacksby intruders outside the network on subscribers within the networkrealm. The visitor location register is a current serving networks‘copy’ of subscriber data needed to provide services. This informationinitially comes from a database which administers mobile subscribers.The mobile services switching center is in charge of ‘circuit switched’connections from UMTS terminals to the network. The gateway mobileservices switching center implements routing functions required based oncurrent location of subscribers. The gateway mobile services alsoreceives and administers connection requests from subscribers fromexternal networks.

The RNCs generally control internal functions of the UTRAN. The RNCsalso provides intermediary services for communications having a localcomponent via a Uu interface connection with a Node B and an externalservice component via a connection between the CN and an externalsystem, for example overseas calls made from a cell phone in a domesticUMTS.

Typically a RNC oversees multiple base stations, manages radio resourceswithin the geographic area of wireless radio service coverage servicedby the Node Bs and controls the physical radio resources for the Uuinterface. In 3GPP, the Iu interface of an RNC provides two connectionsto the CN: one to a packet switched domain and the other to a circuitswitched domain. Other important functions of the RNCs includeconfidentiality and integrity protection.

Various methods of power control for wireless communication systems arewell known in the art. Examples of open and closed loop power controltransmitter systems for wireless communication systems are illustratedin FIGS. 2 and 3, respectively. The purpose of such systems is torapidly vary transmitter power in the presence of a fading propagationchannel and time-varying interference to minimize transmitter powerwhile insuring that data is received at the remote end with acceptablequality.

In communication systems such as Third Generation Partnership Project(3GPP) Time Division Duplex (TDD) and Frequency Division Duplex (FDD)systems, multiple shared and dedicated channels of variable rate dataare combined for transmission. Background specification data for suchsystems are found at 3GPP TS 25.223 v3.3.0, 3GPP TS 25.222 v3.2.0, 3GPPTS 25.224 v3.6 and Volume 3 specifications of Air-Interface for 3GMultiple System Version 1.0, Revision 1.0 by the Association of RadioIndustries Businesses (ARIB). A fast method and system of power controladaptation for data rate changes resulting in more optimal performanceis taught in International Publication Number WO 02/09311 A2, published31 Jan. 2002 and corresponding U.S. patent application Ser. No.09/904,001, filed Jul. 12, 2001 owned by the assignee of the presentinvention.

Where shared channels are utilized, different WTRUs can use the samechannel and channel use by a particular WTRU can be sporadic. Theinventors have recognized that the metric used for adjusting powercontrol in the conventional manner for a specific shared channel may notbe readily available since the relative position of the WTRU may havesubstantially changed from when it last used the specific sharedchannel. Accordingly, it is desirable to provide method and apparatusfor controlling the power of shared channels where there may be sporadicuse of such channels by WTRUs.

For example, the physical channels specified in 3GPP Release 5 (R5) ofUMTS Terrestrial Radio Access Time Division Duplex (UTRA TDD) include aHigh Speed Shared Information Channel (HS-SICH) which operates inconjunction with a High Speed Downlink Shared Channel (HS-DSCH). HS-SICHis a fast Uplink (UL) feedback channel used in UTRA TDD R5 for HighSpeed Down link Packet Access HSDPA operation. The HS-SICH carries a1-bit Ack/Nack message and a several bit long measurement report from aparticular WTRU that received a downlink (DL) transmission on theHS-DSCH.

The HS-DSCH is an HSDPA R5 DL channel used to send packages at very highthroughput to users that use scheduling based upon estimatedinstantaneous channel quality for different users and fast Level 1 (L1)retransmission techniques including hybrid automatic repeat requests(ARQ). Only a single WTRU receives a DL transmission on a HS-DSCH in anygiven Transmission Time Interval (TTI) which is currently specified as10 ms for the HS-DSCH. The particular WTRU that receives thetransmission acknowledges successful/unsuccessful reception of the DLtransmission on the HS-SICH within a specified TTI such that there is a1:1 correlation between TTIs containing a DL HS-DSCH for a particularWTRU and the TTI containing the WTRU's UL acknowledgement. Preferably,the acknowledgment is sent in the ith TTI following the DL transmissionTTI, where i is fixed and greater than 5. Thus in a given TTI, only oneWTRU transmits in the UL HS-SICH, but different WTRUs use the UL HS-SICHfor acknowledging packet reception in other TTIs, respectively.

As with other UL channels, it is desirable to use a loop type powercontrol by a WTRU for determining the necessary UL transmission powerfor the HS-SICH. Conventionally, the WTRU can be configured with anopen-loop power controlled transmitter as shown in FIG. 2 where the WTRUmeasures DL path loss and takes into account UL interference levelsbroadcast or signaled from UTRAN to the WTRUs.

In order to meet certain quality reception targets, a so-called outerloop power control is also preferably implemented in the open loop powercontrol as shown in FIG. 2 where a Tx power adjustment is made inresponse to a metric such as a target Signal to Interference Ratio(SIR). The target SIR is used to control the reception quality of thesignal. A higher target SIR implies better demodulation, but moreinterference created by other users in the system. A lower target SIRimplies lower interference created for other users in the system, butthe demodulation quality is lower. Conventionally, the target SIR isdynamically adjusted by the outer loop power control that updates thedesired value as a function of interference in the system and quality ofthe UL channel.

Outer-loop functionality for a WTRU relies on observations of receivedUL transmissions by a base station such as observing block-error rates(BLER) or received SIRs. If for example the BLER becomes higher thanallowed, such as BLER>0.1 in 3GPP R5, and the user data becomes unusablebecause of too many errors, a higher target SIR is signaled to the WTRUthat the WTRU in turn will apply to adjust its transmit power. However,the time-shared nature of shared channels such as the HS-SICH where aparticular WTRU only transmits in the channel sporadically makes it verydifficult to observe WTRU specific BLER or measured SIR with a frequencyto assure consistent outer loop power control.

To ensure system operation and for simplicity, a high target SIR onHS-SICH accommodating the worst case WTRU with the worst case target SIRcan be chosen in place of outer loop power control where measurement ismade of received UL signals from the particular WTRU. However, theresulting degree of interference makes it difficult to allocate otherchannels into a Time Slot (TS) containing the HS-SICH. Consequently,resources are wasted. The fact that it is desirable to operate severalchannels in a TS containing HS-SICH, for resource efficiency, aggravatesthis problem. Without outer loop power control, code resources in aHS-SICH timeslot are wasted. Generally, if WTRUs cannot achieve reliableUL Tx power on HS-SICH in large cell portions, HSDPA operation in UTRATDD may be heavily compromised. Thus, it is desirable to provide amechanism for UTRA TDD that allows accurate updates of WTRU specifictarget SIR values for HS-SICH operation.

SUMMARY

The invention provides controlled transmitter power in a wirelesscommunication system in which both dedicated and shared channels areutilized. In one embodiment, outer loop transmission power control isprovided for a wireless communication system in which user data issignaled from a network unit in both shared channels available tounspecified wireless transmit receive units (WTRUs) and dedicatedchannels that are assigned for use by a specific WTRU in which the WTRUtransmits data signals on an uplink dedicated channel (UL DCH) andsporadically transmits data signals on an associated uplink sharedchannel (UL SCH). The network unit preferably has a receiver forreceiving UL user data from WTRUs on UL DCHs and at least one UL SCH anda processor for computing target metrics for UL DCHs based on thereception of signals transmitted by a WTRU on an UL DCH associated withan UL SCH usable by the WTRU. A shared channel target metric generatoris provided that is configured to output a respective UL SCH targetmetric derived from each computed UL DCH target metric. Each WTRUpreferably has a processor which computes transmit power adjustments asa function of target metrics for UL channels. The WTRU processors arepreferably configured to compute UL DCH power adjustments for an UL DCHassociated with an UL SCH as a function of UL DCH target metricscomputed by the network unit based on the reception of signalstransmitted by the WTRU on the UL DCH and UL SCH power adjustments forthe associated UL SCH as a function of the respective UL SCH targetmetrics output from the shared channel target metric generator. EachWTRU also has a transmitter operatively associated with the WTRU'sprocessor for transmitting user data on the UL DCH and associated UL SCHat respective power levels corresponding to respective computed UL DCHand UL SCH power adjustments.

Preferably, the target metrics are target signal to interference ratios(SIRs) and the communication system has either open or closed looptransmission power control for WTRU transmissions. The invention isparticularly suited, but not limited for implementation in a UniversalMobile Telecommunications System (UMTS), such as a 3GPP R5 system wherethe SCHs for which SCH target SIRs are generated are High Speed SharedInformation Channels (HS-SICHs) which operate in conjunction with HighSpeed Downlink Shared Channels (HS-DSCHs).

As one alternative, the network unit includes the shared channel targetmetric generator. In that case, for an open loop system, the networkunit preferably includes a transmitter configured to transmit DCH andSCH target SIRs and the WTRUs each preferably include a receiverconfigured to receive respective DCH and SCH target SIRs such that theWTRU's processor computes power adjustments based on received DCH andSCH target SIRs.

For a closed loop system in which the network unit includes the sharedchannel target metric generator, the network unit preferably includes acomponent configured to produce DCH and SCH power step commands as afunction DCH target SIRs computed by the network unit's processor andSCH target SIRs generated by the shared channel target metric generatorand a transmitter configured to transmit DCH and SCH power stepcommands. The WTRUs then each preferably include a receiver configuredto receive respective DCH and SCH power step commands such that theWTRU's processor computes power adjustments based on received DCH andSCH power step commands.

In another alternative, each WTRU includes a shared channel targetmetric generator where the target metrics are target signal tointerference ratios (SIRs). Where the communication system has open looptransmission power control for WTRU transmission, the network unit thenpreferably includes a transmitter configured to transmit DCH target SIRsand each WTRU include a receiver configured to receive respective DCHtarget SIRs such that the WTRU's processor computes power adjustmentsbased on received DCH target SIRs and SCH target SIRs generated by theWTRU's shared channel target metric generator based on received DCHtarget SIRs.

The invention provides a serving wireless transmit receive unit (WTRU)for implementing transmission power control for other WTRUs where userdata is signaled to the serving WTRU by the other WTRUs in both up link(UL) shared channels available to unspecified WTRUs and dedicated ULchannels that are assigned for use by a specific WTRU in which thespecific WTRU transmits data signals on an uplink dedicated channel (ULDCH) and sporadically transmits data signals on an associated uplinkshared channel (UL SCH) and where the other WTRUs each include aprocessor which computes UL channel power adjustments for an UL DCH andan associated UL SCH as a function of UL target metrics computed by theserving WTRU. The serving WTRU preferably includes a receiver forreceiving UL user data from other WTRUs on UL DCHs and at least one ULSCH, a processor for computing target metrics for UL DCHs based on thereception of signals transmitted by a WTRU on an UL DCH associated withan UL SCH usable by the WTRU, and a shared channel target metricgenerator configured to output a respective UL SCH target metric derivedfrom each computed UL DCH target metric.

Preferably, the target metrics are target signal to interference ratios(SIRs). Where the serving WTRU is for use in a Universal MobileTelecommunications System (UMTS), it is preferably configured as a UMTSTerrestrial Radio Access Network (UTRAN) that has either open or closedloop transmission power control for WTRU transmissions and the SCHs forwhich SCH target SIRs are generated are High Speed Shared InformationChannels (HS-SICHs) which operate in conjunction with High SpeedDownlink Shared Channels (HS-DSCHs). For an open loop system, the UTRANpreferably includes a transmitter configured to transmit DCH and HS-SICHtarget SIRs whereby the other WTRUs compute power adjustments based onDCH and HS-SICH target SIRs received from the UTRAN transmitter. For aclosed loop system, the UTRAN preferably includes a component configuredto produce DCH and HS-SICH power step commands as a function DCH targetSIRs computed by the processor and HS-SICH target SIRs generated by theshared channel target metric generator and a transmitter configured totransmit DCH and HS-SICH power step commands whereby the other WTRUscompute power adjustments based on DCH and HS-SICH power step commandsreceived from the UTRAN's transmitter.

The invention also provides a wireless transmit receive unit (WTRU)having a transmission power control for a wireless communication systemin which user data is signaled in both shared channels available tounspecified WTRUs and dedicated channels that are assigned for use by aspecific WTRU in which the WTRU transmits data signals on an uplinkdedicated channel (UL DCH) and sporadically transmits data signals on anassociated uplink shared channel (UL SCH). As such, the WTRU preferablyincludes a receiver for receiving target metrics for the UL DCH thathave been computed based on the reception of signals transmitted by theWTRU on the UL DCH, a shared channel target metric generator configuredto output UL SCH target metrics derived from received UL DCH targetmetrics and a processor which computes power adjustments as a functionof target metrics configured to compute UL DCH power adjustments as afunction of the received UL DCH target metric and UL SCH poweradjustments as a function of UL SCH target metrics output from theshared channel target metric generator. Preferably, the target metricsare target signal to interference ratios (SIRs), so that the processorcomputes power adjustments based on received DCH target SIRs and SCHtarget SIRs generated by the WTRU's shared channel target metricgenerator based on received DCH target SIRs. Preferably, the processoris operatively associated with a transmitter having a combinerconfigured to combine the computed UL DCH power adjustments with the ULDCH transmission data signals for transmission by the WTRU and acombiner configured to combine the computed UL SCH power adjustmentswith the UL SCH transmission data signals for transmission by the WTRU.

The WTRU can be advantageously configured for use in a Universal MobileTelecommunications System (UMTS) that has open loop transmission powercontrol for WTRU transmissions in which the SCHs for which SCH targetSIRs are generated are High Speed Shared Information Channels (HS-SICHs)which operate in conjunction with High Speed Downlink Shared Channels(HS-DSCHs). In such case, the processor preferably computes poweradjustments based on received DCH target SIRs and HS-SICH target SIRsgenerated by the WTRU's shared channel target metric generator based onreceived DCH target SIRs. Also, the processor is preferably operativelyassociated with a transmitter having a combiner configured to combinethe computed UL DCH power adjustments with the UL DCH transmission datasignals for transmission by the WTRU and a combiner configured tocombine the computed UL HS-SICH power adjustments with the UL HS-SICHtransmission data signals for transmission by the WTRU.

Methods of outer loop transmission power control are provided for awireless communication system in which user data is signaled in bothshared channels available to unspecified wireless transmit receive units(WTRUs) and dedicated channels that are assigned for use by a specificWTRU in which the WTRU transmits data signals on an uplink dedicatedchannel (UL DCH) and sporadically transmits data signals on anassociated uplink shared channel (UL SCH). In one method, UL user datais received from WTRUs on UL DCHs and at least one UL SCH and targetmetrics are computed for UL DCHs based on the reception of signalstransmitted by a WTRU on an UL DCH associated with an UL SCH usable bythe WTRU by a network unit. A respective UL SCH target metric is derivedfrom each computed UL DCH target metric. UL DCH power adjustments for anUL DCH associated with an UL SCH are computed by each WTRU as a functionof UL DCH target metrics computed by the network unit based on thereception of signals transmitted by the WTRU on the UL DCH. UL SCH poweradjustments for the associated UL SCH are computed by each WTRU as afunction of the respective UL SCH target metrics output from the sharedchannel target metric generator. User data on the UL DCH and associatedUL SCH is transmitted by each WTRU at respective power levelscorresponding to computed respective UL DCH and UL SCH poweradjustments. The respective UL SCH target metrics can be derived fromeach computed UL DCH target metric by either the network unit or theWTRUs. Preferably, the target metrics are target signal to interferenceratios (SIRs). Also the outer loop power control methods can beimplemented for either open or closed loop transmission power controlfor WTRU transmissions. The methods can be advantageously implemented ina Universal Mobile Telecommunications System (UMTS) where the networkunit is a UMTS Terrestrial Radio Access Network (UTRAN) and the SCHs forwhich SCH target SIRs are generated are High Speed Shared InformationChannels (HS-SICHs) which operate in conjunction with High SpeedDownlink Shared Channels (HS-DSCHs).

The invention includes a method for implementing transmission powercontrol by a serving wireless transmit receive unit (WTRU) for otherWTRUs where user data is signaled to the serving WTRU by the other WTRUsin both up link (UL) shared channels available to unspecified WTRUs anddedicated UL channels that are assigned for use by a specific WTRU inwhich the specific WTRU transmits data signals on an uplink dedicatedchannel (UL DCH) and sporadically transmits data signals on anassociated uplink shared channel (UL SCH) and where the other WTRUs eachcompute UL channel power adjustments for an UL DCH and an associated ULSCH as a function of UL target metrics computed by the serving WTRU. ULuser data is received from other WTRUs on UL DCHs and at least one ULSCH. Target metrics for UL DCHs are computed based on the reception ofsignals transmitted by a WTRU on an UL DCH associated with an UL SCHusable by the WTRU. A respective UL SCH target metric is generatedderived from each computed UL DCH target metric. Preferably, thecomputing and generating of target metrics comprises computing andgenerating of target signal to interference ratios (SIRs). The method isadvantageously implemented in a Universal Mobile TelecommunicationsSystem (UMTS) where the serving WTRU is configured as a UMTS TerrestrialRadio Access Network (UTRAN) that implements open or closed looptransmission power control for WTRU transmissions and the SCHs for whichSCH target SIRs are generated are High Speed Shared Information Channels(HS-SICHs) which operate in conjunction with High Speed Downlink SharedChannels (HS-DSCHs). In an open loop system, DCH and HS-SICH target SIRsare preferably transmitted whereby the other WTRUs compute poweradjustments based on DCH and HS-SICH target SIRs received from theUTRAN. In a closed loop system, DCH and HS-SICH power step commands arepreferably produced as a function DCH target SIRs and HS-SICH targetSIRs and DCH and HS-SICH power step commands are transmitted whereby theother WTRUs compute power adjustments based on DCH and HS-SICH powerstep commands received from the UTRAN.

Also provided is a method of transmission power control for a wirelesstransmit receive unit (WTRU) used in a wireless communication system inwhich user data is signaled in both shared channels available tounspecified WTRUs and dedicated channels that are assigned for use by aspecific WTRU in which the WTRU transmits data signals on an uplinkdedicated channel (UL DCH) and sporadically transmits data signals on anassociated uplink shared channel (UL SCH). Target metrics for the UL DCHare received that have been computed based on the reception of signalstransmitted by the WTRU on the UL DCH. UL SCH target metrics aregenerated derived from received UL DCH target metrics. UL DCH poweradjustments are computed as a function of the received UL DCH targetmetric and UL SCH power adjustments are computed as a function of UL SCHtarget metrics. Preferably, the target metrics are target signal tointerference ratios (SIRs), so that the WTRU computes power adjustmentsbased on received DCH target SIRs and SCH target SIRs generated by theWTRU based on received DCH target SIRs and the WTRU combines thecomputed UL DCH power adjustments with the UL DCH transmission datasignals for transmission by the WTRU and combines the computed UL SCHpower adjustments with the UL SCH transmission data signals fortransmission by the WTRU. The method can be advantageously implementedfor use in a Universal Mobile Telecommunications System (UMTS) thatimplements open loop transmission power control for WTRU transmissions.In such case, the SCHs for which SCH target SIRs are generated arepreferably High Speed Shared Information Channels (HS-SICHs) whichoperate in conjunction with High Speed Downlink Shared Channels(HS-DSCHs), wherein the WTRU computes power adjustments based onreceived DCH target SIRs and HS-SICH target SIRs generated by the WTRUbased on received DCH target SIRs, combines the computed UL DCH poweradjustments with the UL DCH transmission data signals for transmissionby the WTRU and combines the computed UL HS-SICH power adjustments withthe UL HS-SICH transmission data signals for transmission by the WTRU.

Other objects and advantages will be apparent to those of ordinary skillin the art based upon the following description of presently preferredembodiments of the invention.

BRIEF DESCRIPTION OF THE DRAWING(S)

FIG. 1 shows an overview of a system architecture of a conventional UMTSnetwork.

FIG. 2 is a schematic diagram of a conventional open loop power controlsystem for a wireless communication system which implements outer looppower control via a target SIR metric.

FIG. 3 is a schematic diagram of a conventional closed loop powercontrol system for a wireless communication system which implementsouter loop power control via a target SIR metric.

FIG. 4 is a schematic diagram of an open loop power control system for awireless communication utilizing both a dedicated channel and a highspeed shared channel made in accordance with the teaching of the presentinvention.

FIG. 5 is a schematic diagram of an alternate embodiment of a powercontrol system for a wireless communication utilizing both a dedicatedchannel and a high speed shared channel made in accordance with theteaching of the present invention.

FIG. 6 is a schematic diagram of a closed loop power control system fora wireless communication utilizing both a dedicated channel and a highspeed shared channel made in accordance with the teaching of the presentinvention.

TABLE OF ACRONYMS 2G second generation mobile radio system standard 3GPPthird generation partnership project ARIB association of radioindustries businesses ARQ automatic repeat request BLER block error rateCN core network DCH dedicated channel DL downlink ETSI SMG Europeantelecommunications standard institute- special mobile group FDDfrequency division duplex GPRS general packet radio service GSM globalsystem for mobile telecommunications HS high speed HSDPA high speed downlink packet access HS-DSCH high speed downlink shared channel HS-SICHhigh speed shared information channel L1 level 1 PSTN public switchedtelephone network R5 release 5 RNCs radio network controllers RRC radioresource control SIR signal to interference ratio TDD time-divisionduplex TS time slot TTI transmission time interval Tx transmission UEsuser equipments UL uplink UL DCH uplink dedicated channel UL SCH uplinkshared channel UMTS universal mobile telecommunication system UTRA TDDUMTS terrestrial radio access time division duplex UTRAN UMTSterrestrial radio access network WTRUs wireless transmit receive units

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

Conventional power control methods for wireless systems such as 3GPPutilize so-called inner and outer loops. The power control system isreferred to as either open or closed dependent upon whether the innerloop is open or closed. The outer loops of both types of systems areclosed loops.

Pertinent portions of an open loop power control system having a“transmitting” communication station 10 and a “receiving” communicationstation 30 are shown in FIG. 2. Both stations 10, 30 are transceivers.Typically one is a base station, called a Node B in 3GPP, and the othera type of WTRU, called a user equipment UE in 3GPP. For clarity, onlyselected components are illustrated and the invention is described interms of a preferred 3GPP system, but the invention has application towireless communication systems in general, even such systems thatperform ad hoc networking where WTRUs communicate between themselves.Power control is important to maintain quality signaling for multipleusers without causing excessive interference.

The transmitting station 10 includes a transmitter 11 having a data line12 which transports a user data signal for transmission. The user datasignal is provided with a desired power level which is adjusted byapplying a transmit power adjustment from an output 13 of a processor 15to adjust the transmission power level. The user data is transmittedfrom an antenna system 14 of the transmitter 11.

A wireless radio signal 20 containing the transmitted data is receivedby the receiving station 30 via a receiving antenna system 31. Thereceiving antenna system will also receive interfering radio signals 21which impact on the quality of the received data. The receiving station30 includes an interference power measuring device 32 to which thereceived signal is input which device 32 outputs measured interferencepower data. The receiving station 30 also includes a data qualitymeasuring device 34 into which the received signal is also input whichdevice 34 produces a data quality signal. The data quality measuringdevice 34 is coupled with a processing device 36 which receives thesignal quality data and computes target signal to interference ratio(SIR) data based upon a user defined quality standard parameter receivedthrough an input 37.

The receiving station 30 also includes a transmitter 38 which is coupledwith the interference power measuring device 32 and the target SIRgenerating processor 36. The receiving station's transmitter 38 alsoincludes inputs 40, 41, 42 for user data, a reference signal, andreference signal transmit power data, respectively. The receivingstation 30 transmits its user data and the control related data andreferences signal via an associated antenna system 39.

The transmitting station 10 includes a receiver 16 and an associatedreceiving antenna system 17. The transmitting station's receiver 16receives the radio signal transmitted from the receiving station 30which includes the receiving station's user data 44 and the controlsignal and data 45 generated by the receiving station 30.

The transmitting station's transmitter's processor 15 is associated withthe transmitting station's receiver 16 in order to compute a transmitpower adjustment. The transmitter 11 also includes a device 18 formeasuring received reference signal power which device 18 is associatedwith path loss computing circuitry 19.

In order to compute the transmit power adjustment, the processor 15receives data from a target SIR data input 22 which carries the targetSIR data generated by the receiver station's target SIR generatingprocessor 36, an interference power data input 23 which carries theinterference data generated by the receiving station's interferencepower measuring device 32, and a path loss data input 24 which carries apath loss signal that is the output of the path loss computing circuitry19. The path loss signal is generated by the path loss computingcircuitry 19 from data received via a reference signal transmit powerdata input 25 which carries the reference signal transmit power dataoriginating from the receiving station 30 and a measured referencesignal power input 26 which carries the output of the reference signalpower measuring device 18 of the transmitter 11. The reference signalmeasuring device 18 is coupled with the transmitting station's receiver16 to measure the power of the reference signal as received from thereceiving station's transmitter 38. The path loss computing circuitry 19preferably determines the path loss based upon the difference betweenthe known reference power signal strength conveyed by input 25 and themeasured received power strength conveyed by input 26.

Interference power data, reference signal power data and target SIRvalues are signaled to the transmitting station 10 at a ratesignificantly lower than the time-varying rate of the propagationchannel and interference. The “inner” loop is the portion of the systemwhich relies on the measured interface. The system is considered “openloop” because there is no feedback to the algorithm at a rate comparableto the time-varying rate of the propagation channel and interferenceindicating how good the estimates of minimum required transmitter powerare. If required transmit power level changes rapidly, the system cannotrespond accordingly to change the power adjustment in a timely manner.

With respect to the outer loop of the open loop power control system ofFIG. 2, at the remote receiver station 30, the quality of the receiveddata is evaluated via the measuring device 34. Typical metrics fordigital data quality are bit error rate and block error rate.Computation of these metrics requires data accumulated over periods oftime significantly longer than the period of the time-varyingpropagation channel and interference. For any given metric, there existsa theoretical relationship between the metric and received SIR. Whenenough data has been accumulated in the remote receiver to evaluate themetric, it is computed and compared with the desired metric(representing a desired quality of service) in processor 36 and anupdated target SIR is then output. The updated target SIR is that value(in theory) which applied in the transmitter inner loop would cause themeasured metric to converge to the desired value. Finally, the updatedtarget SIR is passed, via the receiving station transmitter 38 and thetransmitting station receiver 16, to the transmitter 11 for use in itsinner loop. The update rate of target SIR is bounded by the timerequired to accumulate the quality statistic and practical limits on thesignaling rate to the power-controlled transmitter.

With reference to FIG. 3, a communication system having a transmittingstation 50 and a receiving station 70 which employs a closed loop powercontrol system is illustrated.

The transmitting station 50 includes a transmitter 51 having a data line52 which transports a user data signal for transmission. The user datasignal is provided with a desired power level which is adjusted byapplying a transmit power adjustment from an output 53 of a processor 55to adjust the power level. The user data is transmitted via an antennasystem 54 of the transmitter 51.

A wireless radio signal 60 containing the transmitted data is receivedby the receiving station 70 via a receiving antenna system 71. Thereceiving antenna system will also receive interfering radio signals 61which impact on the quality of the received data. The receiving station70 includes an interference power measuring device 72 to which thereceived signal is input which device 72 outputs measured SIR data. Thereceiving station 70 also includes a data quality measuring device 73into which the received signal is also input which device 73 produces adata quality signal. The data quality measuring device 73 is coupledwith a processor 74 which receives the signal quality data and computestarget signal to interference ratio (SIR) data based upon a user definedquality standard parameter received through an input 75.

A combiner 76, preferably a substracter, compares the measured SIR datafrom the device 72 with the computed target SIR data from the processor74, preferably by subtracting, to output an SIR error signal. The SIRerror signal from the combiner 76 is input to processing circuitry 77which generates step up/down commands based thereon.

The receiving station 70 also includes a transmitter 78 which is coupledwith the processing circuitry 77. The receiving station's transmitter 78also includes an input 80 for user data. The receiving station 70transmits its user data and the control related data via an associateantenna system 79.

The transmitting station 50 includes a receiver 56 and an associatedreceiving antenna system 57. The transmitting station's receiver 56receives the radio signal transmitted from the receiving station 70which includes the receiving station's user data 84 and the control data85 generated by the receiving station.

The transmitting station's transmitter's processor 55 has an input 58associated with the transmitting station's receiver 16. The processor 55receives the up/down command signal through input 58 and computes thetransmit power adjustments based thereon.

With respect to the inner loop of the closed loop power control system,the transmitting station's transmitter 51 sets its power based uponhigh-rate “step-up” and “step-down” commands generated by the remotereceiving station 70. At the remote receiving station 70, the SIR of thereceived data is measured by the measuring device 72 and compared with atarget SIR value generated by the processor 74 via combiner 76. Thetarget SIR is that value (in theory) which, given that the data isreceived with that value, results in a desired quality of service. Ifthe measured received SIR is less than the target SIR, a “step-down”command is issued by the processing circuitry 77, via the receivingstation's transmitter 78 and the transmitting station's receiver 56, tothe transmitter 51, otherwise a “step-up” command is issued. The powercontrol system is considered “closed-loop” because of the high-ratefeedback of the “step-up” and “step-down” commands which can react inreal time to the time-varying propagation channel and interference. Ifrequired transmit power level changes due to time varying interferenceand propagation, it quickly responds and adjusts transmit poweraccordingly.

With respect to the outer loop of the closed loop power control system,the quality of the received data is evaluated in the receiving station70 by the measuring device 73. Typical metrics for digital data qualityare bit error rate and block error rate. Computation of these metricsrequires data accumulated over periods of time significantly longer thanthe period of the time-varying propagation channel and interference. Forany given metric, there exists a theoretical relationship between themetric and received SIR. When enough data has been accumulated in theremote receiver to evaluate the metric, it is computed and compared withthe desired metric (representing a desired quality of service) by theprocessor 74 and an updated target SIR is then output. The updatedtarget SIR is that value (in theory) which applied in the receiveralgorithm would cause the measured metric to converge to the desiredvalue. The updated target SIR is then used in the inner loop todetermine the direction of the step up/down commands sent to thetransmitting station's power scale generating processor 55 to controlthe power of the transmitter 51.

In both open and closed power control systems, outer-loop functionalityfor the transmitting station 10, 50 relies on observations of receivedtransmissions by the receiving station 30, 70 such as observingblock-error rates (BLER) or received SIRs. If for example the BLERbecomes higher than allowed, such as BLER>0.1 in 3GPP R5, and the userdata becomes unusable because of too many errors, a higher target SIR iscomputed that causes the transmitting station 10, 50 in turn to adjustits transmit power. However, the time-shared nature of shared channelssuch as the HS-SICH in 3GPP R5 where a particular WTRU only transmits inthe channel sporadically makes it very difficult to observe WTRUspecific BLER or measured SIR with a frequency to assure consistentouter loop power control.

With reference to FIGS. 4, 5 and 6, several modified variations ofconventional power control system are illustrated that provides forouter-loop power control operation for a shared channel such as ULHS-SICH and an associated dedicated channel (DCH). These modifiedsystems take advantage of the availability of more regular observationsof the DCH. In order to set, a metric, such as a target SIR, for theshared channel, the target SIR for the associated DCH is used as a basisof derivation. For example, the target SIR for the HS-SICH for aparticular WTRU is in accordance with the invention derived from thetarget SIR computed for the associated DCH. The derivation is preferablybased on a predetermined mathematical relationship, which can inappropriate circumstances simply be equality, in which case the samecomputed SIR for the DCH is used for the HS-SICH power control.Alternatively, a mapping table based upon environments can be used toderive a target SIR on HS-SICH from the target SIR applied on the DCH.Accordingly, whenever the target SIR on the DCH is changed for aparticular WTRU, the target SIR on the HS-SICH for that WTRU is updatedaccordingly in order to ensure reliable operation.

During HSDPA operation in a 3GPP R5 system, a WTRU is in a CELL_DCHstate where it uses a relatively low-rate duplex DCH for the purpose ofRRC signaling control and user-plane data. Every WTRU has such alow-rate DCH associated with the HS-SICH and on this DCH, outer looppower control is used to dynamically adjust the target SIR on DCH andthe continuous usage (once every single or every second frame) of thisDCH ensures that BLER and measured SIR for UL are meaningful. Even ifHS-SICH and the UL portion of the DCH are potentially allocated indifferent UL TSs, the target SIR on the associated DCH is very heavilycorrelated with an target SIR on HS-SICH, because it primarily dependson the WTRU channel environment and WTRU speed which is the same forboth types of channels. Also, the UL interference levels, which can bedifferent in different TSs, are already taken into account by otherpower control parameters that provide compensation therefor. Thus, theinvention uses the target SIR on UL DCH that is accurately updated basedupon a reliable Outer Loop Power Control functionality to set or toderive needed target SIR on UL HS-SICH for a particular WTRU.

The invention enables one to obtain accurate target SIRs from Outer LoopPower Control functionality that supervises DCH operation. By comparingthe processing gain, payload and required BLER for the HS-SICH to thatof the DCH, basic principles are applied to derive the recommendedtransmit power offset between the two channels. This derived offset canbe performed either in the transmitting station or the receivingstation, which in the case of a preferred 3GPP R5 embodiment for aHS-SICH correspond respectively to a UE and UTRAN, respectively.

FIGS. 4 and 5 illustrate modified open loop power control system for awireless communication system made in accordance with the teaching ofthe present invention where like components that correspond to theconventional system shown in FIG. 2 are indicated with like referencenumerals. For the example of an UL shared channel, such as the HS-SICH,the transceiver 10 is a WTRU and the component 30 represents a servicingnetwork, such as a 3GPP R5 UTRAN.

In the case of the FIGS. 4 and 5 embodiments, the User Data pathillustrated in FIG. 2, carries the data of the DCH which is associatedwith the shared channel. Data line 12 of FIG. 2, which transports userdata for transmission from the WTRU, is identified as data line 12 d inFIGS. 4 and 5 to signify the line for the UL data of the DCH. The UL DCHdata signal is provided with a desired power level which is adjusted byapplying a transmit power adjustment from an output 13 d of a processor15 to adjust the transmission power level. Data line 40 of FIG. 2, whichtransports user data for transmission to the WTRU, is identified as line40 d in FIGS. 4 and 5 to signify the line for the DL data of the DCH.

A data line 12 s is provided to transport the UL data of the HS-SICH inthe WTRU 10. The UL HS-SICH data signal is provided with a desired powerlevel which is adjusted by applying a transmit power adjustment from anoutput 13 s of a processor 15 to adjust the transmission power level. Inthe receiving station 30, a receiver 46 is provided to output theseparate DCH and HS-SICH channels.

The power adjustment in the example WTRU 10, performed by thetransmitter's processor 15 is preferably made in a conventional mannerfor each of the channels DCH and HS-SICH, respectively. In order tocompute the respective transmit power adjustments, the processor 15receives data from a respective target SIR data input 22 d, 22 s whichcarries the respective DCH and HS-SICH target SIR data, an interferencepower data input 23 which carries the interference data generated by thereceiving station's interference power measuring device 32, and a pathloss data input 24 which carries a path loss signal that is the outputof the path loss computing circuitry 19.

The target SIR DCH is preferably generated in the conventional manner byevaluating the quality of the received DCH UL data via the measuringdevice 34. Typical metrics for digital data quality are bit error rateand block error rate. Computation of these metrics requires dataaccumulated over periods of time significantly longer than the period ofthe time-varying propagation channel and interference. For any givenmetric, there exists a theoretical relationship between the metric andreceived SIR. When enough data has been accumulated in the remotereceiver to evaluate the metric, it is computed in processor 36 andcompared with the desired metric (representing a desired quality ofservice) provided by input 37 and an updated target SIR DCH is thenoutput. The updated target SIR DCH is that value (in theory) whichapplied in the transmitter inner loop would cause the measured metric toconverge to the desired value. Finally, the updated target SIR DCH ispassed, via the receiving station transmitter 38 and the transmittingstation receiver 16, to the transmitter 11 for use in its inner loop forthe DCH. The update rate of target SIR DCH is bounded by the timerequired to accumulate the quality statistic and practical limits on thesignaling rate to the power-controlled transmitter.

Due to the sporadic and shared use nature of the HS-SICH, attempting tocompute a target SIR for the HS-SICH in the conventional manner isimpractical. Accordingly, the outer loop power control for the HS-SICHincludes a HS-SICH target SIR derivation device 27 to which the targetSIR DCH is input and from which the target SIR HS-SICH is output. TheHS-SICH target SIR derivation device 27 preferably sets the relationshipbetween target SIR on DCH and target SIR on HS-SICH either as 1:1 or anyother predefined mathematical relationship, or as taken from a mappingtable.

FIG. 4 illustrates a preferred embodiment where the HS-SICH target SIRderivation device 27 is included in the receiving station 30. Where theinvention is implemented in a UMTS system, the transmitting station 10preferably represents a WTRU and the receiving station 30 preferablyrepresents network components of a UTRAN. The target SIR HS-SICH is thenderived in the UTRAN and passed, via the UTRAN's transmitter 38 and theWTRU's receiver 16, to the WTRU's transmitter's processor 15 via theinput 22 s for use in the inner loop for the HS-SICH.

FIG. 5 illustrates an alternate embodiment where the HS-SICH target SIRderivation device 27 is included in the transmitting station 10. In thatcase, the target SIR DCH that is passed, via the receiving stationtransmitter 38 and the WTRU's receiver 16, and fed to the derivationdevice 27 in the WTRU's transmitter 11, which in turn derives theHS-SICH target SIR and feeds it to the processor 15 via the input 22 sfor use in the inner loop for the HS-SICH.

FIG. 6 illustrates a modified closed loop power control system for awireless communication system made in accordance with the teaching ofthe present invention where like components that correspond to theconventional system shown in FIG. 3 are indicated with like referencenumerals. For the example of an UL shared channel, such as the HS-SICH,the transceiver 50 is a WTRU and the component 70 represents a servicingnetwork, such as a 3GPP R5 UTRAN.

In the case of the FIG. 6 embodiment, the User Data path illustrated inFIG. 3 carries the data of the DCH, which is associated with the sharedchannel. Data line 52 of FIG. 3, which transports user data fortransmission from the WTRU, is identified as line 52 d in FIG. 6 tosignify the line for the UL data of the DCH. The UL DCH data signal isprovided with a desired power level which is adjusted by applying atransmit power adjustment from an output 53 d of a processor 55 toadjust the transmission power level. Data line 80 of FIG. 3, whichtransports user data for transmission to the WTRU, is identified as line80 d in FIG. 6 to signify the line for the DL data of the DCH.

In the FIG. 6 embodiment, a data line 52 s is provided to transport theUL data of the HS-SICH in the WTRU 10. The UL HS-SICH data signal isprovided with a desired power level, which is adjusted by applying atransmit power adjustment from an output 53 s of a processor 55 toadjust the transmission power level. In the receiving station 70, areceiver 86 is provided to output the separate DCH and HS-SICH channels.Where the invention is implemented in a UMTS system, the transmittingstation 50 preferably represents a WTRU and the receiving station 70preferably represents network components of a UTRAN.

The power adjustment in the example WTRU 50 performed by thetransmitter's processor 55 is preferably made in a conventional mannerfor each of the channels DCH and HS-SICH, respectively. In order tocompute the respective transmit power adjustments, the processor 15receives respective up/down command signals through inputs 58 d and 58 sand computes the respective transmit power adjustments based thereon.

With respect to the inner loop of the closed loop power control system,the transmitting station's transmitter 51 sets its power based uponhigh-rate “step-up” and “step-down” commands generated by the receivingstation 70. At the receiving station 70, the SIR of the received DCHdata is measured by the measuring device 72 and compared with a targetSIR DCH value generated by the processor 74 via combiner 76 d. If themeasured received SIR DCH is less than the target SIR DCH, a DCH“step-down” command is issued and passed by the processing circuitry 77,via the receiving station's transmitter 78 and the transmittingstation's receiver 56, to the transmitter 51 via input 58 d, otherwise aDCH “step-up” command is issued. The power control system is considered“closed-loop” because of the high-rate feedback of the “step-up” and“step-down” commands which can react in real time to the time-varyingpropagation channel and interference. If required transmit power levelchanges due to time varying interference and propagation, it quicklyresponds and adjusts transmit power accordingly.

With respect to the outer loop of the closed loop power control systemof FIG. 6, the quality of the received DCH data is evaluated in thereceiving station 70 by the measuring device 73. Typical metrics fordigital data quality are bit error rate and BLER. Computation of thesemetrics requires data accumulated over periods of time significantlylonger than the period of the time-varying propagation channel andinterference. For any given metric, there exists a theoreticalrelationship between the metric and received SIR DCH. When enough datahas been accumulated in the remote receiver to evaluate the metric, itis computed and compared with the desired metric (representing a desiredquality of service) by the processor 74 and an updated target SIR DCH isthen output. The updated target SIR DCH is then used in the inner loopto determine the direction of the DCH step up/down commands sent to thetransmitting station's power adjustment generating processor 55 tocontrol the power of the transmitter 51.

Due to the sporadic and shared use nature of the HS-SICH, attempting tocompute a target SIR for the HS-SICH in the conventional manner isimpractical. Accordingly, FIG. 6 illustrates a preferred embodimentwhere the outer loop power control for the HS-SICH includes a HS-SICHtarget SIR derivation device 87 to which the target SIR DCH is input andfrom which the target SIR HS-SICH is output. The HS-SICH target SIRderivation device 27 preferably sets the relationship between target SIRon DCH and target SIR on HS-SICH either as 1:1 or any other predefinedmathematical relationship, or as taken from a mapping table. The targetSIR HS-SICH value generated by the device 87 is and compared viacombiner 76 s with SIR of the received DCH data is measured by themeasuring device 72 or a derivative thereof. Alternatively, the SIR ofthe received HS-SICH is measured and compared with the target SIRHS-SICH. If the compared value is less than the target SIR HS-SICH, aHS-SICH “step-down” command is issued and passed by the processingcircuitry 77, via the receiving station's transmitter 78 and thetransmitting station's receiver 56, to the transmitter 51 via input 58s, otherwise a HS-SICH “step-up” command is issued.

Thus, as described above, reliable Outer Loop Power Controlfunctionality on HS-SICH is achieved for radio resource usage efficiencyin HSDPA for UTRA TDD. The invention thus provides a new relationshipbetween target SIR settings on DCH and HS-SICH for particular WTRUs andall usages thereof.

The foregoing description makes references to HSDPA in UTRA TDD as anexample only and not as a limitation. The invention is applicable toother systems of wireless communication including dedicated and sharedchannels. Other variations and modifications consistent with theinvention will be recognized by those of ordinary skill in the art.

What is claimed is:
 1. A wireless transmit receive unit (WTRU)comprising: a transmitter configured to transmit on a first channel anda second channel; wherein the second channel is an uplink sharedchannel; a receiver configured to respectively receive first powercommands for the first channel and second power commands for the uplinkshared channel; and a processor configured to determine a first channeltransmission power level in response to the first power commands and notthe second power commands, and to determine an uplink shared channeltransmission power level in response to the second power commands andnot the first power commands.
 2. The WTRU of claim 1 wherein each of thefirst and second power commands indicate one of a step up or a step downin transmission power level.
 3. The WTRU of claim 1 wherein the uplinkshared channel is transmitted sporadically.
 4. The WTRU of claim 1wherein the first channel is assigned to the WTRU.
 5. The WTRU of claim1 wherein the first channel is a dedicated channel.
 6. A methodcomprising: transmitting, by a wireless transmit receive unit (WTRU), ona first channel and a second channel; wherein the second channel is anuplink shared channel; respectively receiving, by the WTRU, first powercommands for the first channel and second power commands for the uplinkshared channel; and determining, by the WTRU, a first channeltransmission power level in response to the first power commands and notthe second power commands, and to determine an uplink shared channeltransmission power level in response to the second power commands andnot the first power commands.
 7. The method of claim 6 wherein each ofthe first and second power commands indicate one of a step up or a stepdown in transmission power level.
 8. The method of claim 6 wherein theuplink shared channel is transmitted sporadically.
 9. The method ofclaim 6 wherein the first channel is assigned to the WTRU.
 10. Themethod of claim 6 wherein the first channel is a dedicated channel. 11.A network node comprising: a receiver configured to receive a firstchannel and a second channel from a wireless transmit receive unit(WTRU); wherein the second channel is an uplink shared channel; and atransmitter configured to respectively transmit first power commands forthe first channel and second power commands for the uplink sharedchannel; wherein the first power commands are to adjust a transmissionpower level of the first channel and not the uplink shared channel, andthe second power commands are to adjust a transmission power level ofthe uplink shared channel and not the first channel; wherein thereceiver is further configured to receive a transmission power adjustedfirst channel and a transmission power adjusted uplink shared channelfrom the WTRU.
 12. The network node of claim 11 wherein each of thefirst and second power commands indicate one of a step up or a step downin transmission power level.
 13. The network node of claim 11 whereinthe uplink shared channel is received sporadically.
 14. The network nodeof claim 11 wherein the first channel is assigned to the WTRU.
 15. Thenetwork node of claim 11 wherein the first channel is a dedicatedchannel.